Orthogonal Frequency-Division Multiple Access (OFDMA) is a proven access technique for efficient user and data multiplexing in the frequency domain. One example of a system employing OFDMA is Long-Term Evolution (LTE), LTE is the next step in cellular Third-Generation (G) systems, which represents basically an evolution of previous mobile communications standards such as Universal Mobile Telecommunication System (UMTS) and Global System for Mobile Communications (GSM). It is a Third Generation Partnership Project (3GPP) standard that provides throughputs up to 50 Mbps in uplink and up to 100 Mbps in downlink. It uses, scalable bandwidth from 1.4 to 20 MHz in order to suit the needs of network operators that have different bandwidth allocations. LTE is also expected to improve spectral efficiency in networks, allowing carriers to provide more data and voice services over a given bandwidth. Other wireless standards like WiFi (IEEE 802.11) or WiMAX (IEEE 802.16) also employ OFDMA.
One of the most serious issues when deploying single-frequency wireless Orthogonal Frequency Division Multiplexing (OFDM) networks is the increased interference suffered by users at the cell edges which require specialized techniques. One of the simpler approaches is so-called inter-Cell Interference Coordination (ICIC), wherein frequency resources are statically partitioned into several “chunks” designated for different cells as disclosed in “LTE, the UMTS Long Term Evolution: From Theory to Practice”, John Wiley & Sons (2nd edition), p. 28, 2011.
Other more advanced approaches include semi-static tinge-domain and/or frequency domain coordination of the cells, in such a way that time and/or frequency resources are coordinated among a given cluster of neighbour cells so as to avoid interferences towards a given user. These approaches give rise to either Carrier Aggregation-based enhanced Inter-Cell Interference Coordination (CA-eICIC), or Almost Blank Subframes-based enhanced Inter-Cell Interference Coordination (ABS-eICIC), both described in “LTE, the UMTS Long Term Evolution: From Theory to Practice”, John Wiley & Sons (2nd edition), p. 701, 2011.
Previous solutions suffer the drawback of how large the coordination cluster should be. Too large clusters lead to very high complexity in resources, coordination (as well as signalling exchange between cells), while smaller clusters lead to suboptimal performance and significant inter-cluster interference. In addition, interference from cells outside any coordination cluster will destroy part of the expected advantage if it is received with sufficiently strong signal level.
CA-based eICIC solutions require at least two component carriers to be aggregated at the receiver side, and do not foresee coordination beyond two neighbour cells unless complex combinations of frequency bands are allowed. ABS-based eICIC suffers the drawback of requiring complex patterns of muted/unmuted subframes that may not scale with increasingly larger clusters. Moreover, cells not operating in ABS mode will cause harmful interference as their transmission occasions will fully collide with those of the protected subframes.
Solutions based on successive interference cancellation (SIC) at the receivers are mainly focused on interference cancellation of control channels, as these have a known structure and do not require additional signalling from the network. However data channels can present multiple formats depending on multi-antenna use, modulation and coding scheme, etc. and thus require significant signalling from the network for the receivers to perform SIC. This translates into higher complexity at the device side as well as lower chances to cancel interference beyond one or two dominant interferers.
Other solutions belong to so-called Coordinated Multi-Point (CoMP) techniques, where data-plane transmission or reception from/to multiple cells is coordinated so as to avoid interferences. The main difference with respect to ICIC/eICIC solutions is that the former ones involve the data plane while the latter ones only deal with the control plane. Data plane coordination is much more costly in terms of network resources and information exchange between the network nodes, thus leading to complex solutions. In addition, interference from cells outside a coordination cluster is very difficult to mitigate.
Therefore, there is a need in the state of the art for more efficient ways to deal with inter-cell interference in order to enable low-complex inter-cell interference coordination in OFDM wireless networks.